Conventionally, an electric current control device that controls an electric current supplied to an electric motor via an inverter is known.
For example, in a patent document, JP H08-191600 A (patent document 1), for avoiding a saturation of an output voltage of the inverter by controlling the d-axis/q-axis voltage instruction values, i.e., by having a constant value for the sum of squares of the d-axis voltage instruction value and the q-axis voltage instruction value, the voltage of each of the d-axis and the q-axis is restricted.
When it comes to a control of the d-axis voltage instruction value and the q-axis voltage instruction value, i.e., a control of having a constant square sum of the d-axis voltage instruction value and the q-axis voltage instruction value, as disclosed in the patent document 1, the variation of the d-axis voltage instruction value may incur the variation of the q-axis voltage instruction value, thereby causing a change of a q-axis current and also causing a noise/vibration.